Mixed flow multiple pump



Sept. 14, 1954 T. R. THOREN ET AL 2,688,925

MIXED FLOW MULTIPLE P-UMP Filed Sept. 27, 1950 4 Sheets-Sheet l ZHVE'HZUPE 7728062 02 812 Tkofiezz J 01222 Elva array y $6 44; HLLHE Sept. 14, 1954 T. R. THOREN ET MIXED FLOW MULTIPLE PUMP 4 Sheets-Sheet 2 Filed Sept. 27, 1950 15775 77227? 5 Theodore 72. Thor'n Filed Sept. 27, 1950 T.' R. THOREN ET AL MIXED FLOW MULTIPLE PUMP 4 Sheets-Sheei 3 Q 3 r a w v H g H g I five a m 1. 8 I

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MIXED FLOW MULTIPLE PUMP Filed Sept. 27, 1950 4 Sheets-Sheet 4 Theodore 7E. Thbren JZJhn F Murray Z7 57 3:; 5275 5 Patented Sept. 14, 1954 MIXED FLOW MULTIPLE PUMP Theodore R. Thoren, Chagrin Falls, and John F. Murray, Macedonia, Ohio, assignors to Thompson Products, tion of Ohio Inc., Cleveland, Ohio, a corpora- Application September 27, 1950, Serial No. 187,077

3 Claims.

This invention relates to an aircraft fuel system and relates particularly to a mixed flow multiple pump for incorporation within such a system for pressuring the volatile aircraft fuel toward the aircraft engine. Such a pump finds particular utility during high altitude operation of the aircraft.

Due to the volatile nature of aircraft fuel, abrupt pressure drops within the piping and fluid conduits should be avoided lest vapor be evolved in quantities great enough to cause vapor lock.

One such abrupt pressure drop occurs in the pump between the inlet fitting and the pumping chambers. This loss is commonly known as inlet loss." Such loss occurs in vane pumps, gear pumps, and, in fact, most positive displacement types wherein the fuel must flow in against rotating pumping elements. Vapor evolved as a result of such pressure loss reduces the volumetric efliciency of the pump. The way to overcome such pressure loss is to supply additional pressure at some suitable point in the circuit. We propose to supply this pressure increment by means of a low inlet loss centrifugal pumping element in series and ahead of the positive displacement pump.

It is a feature of the present invention to provide a mixed flow multiple pump for incorporation with an aircraft fuel system as an in line pump-that is, the pump is in the fuel line between the fuel cell and the engine-driven main fuel pump. The pump of this invention may be driven by the aircraft engine, or from an auxiliary power source such as an electric motor. The pump is a two-stage type; the first, a mixed fiow centrifugal impeller stage, and the second, a positive displacement stage employing sliding vane mechanism or gear pumping mechanism. The mechanism of the first stage supplies fuel to the second stage under increased or boost pressure. The second stage increases the pressure-on the fuel to the engine-driven main fuel pump.

A booster pump having highly efficient vapor separating characteristics may be incorporated in the fuel system at the fuel cell for pressuring fuel to the mixed flow multiple pump. The mixed flow multiple pump may be operated as the main engine-driven fuel pump, or may be installed as previously mentioned, as an auxiliary or booster pump to the main fuel pump. When installed in the fuel system with the main fuel pump and a fuel cell booster pump, the fuel may by-pass the mixed fiow multiple pump during inoperation of the pump by means of bypass valves which are opened under pressure of the fuel being pumped by the fuel cell booster and/or by the engine driven fuel pump. A similar by-pass system is provided in the fuel cell booster pump so that in the event of inoperation of that pump, fuel may by-pass the pump and flow to the mixed fiow multiple pump and main fuel pump.

The mixed fiow multiple pump has the advantage of low inlet losses, whichfactor provides for improved pumping performance at the low atmospheric pressures encountered at high altitudes and thereby is enabled to provide the main fuel pump with a continuous fiow of pressured fuel.

Accordingly, it is an object of this invention to provide an improved fuel system for aircraft engines.

Another object of this invention is to provide a mixed flow multiple pump for incorporation in an aircraft fuel system, the pump having two stages, the first for avoiding inlet pressure losses and for pressuring fluid to the inlet of the second stage, or positive displacement pumping stage.

It is another object of this invention to provide a fuel pump for aircraft engines which may be driven by the aircraft engine, or by auxiliary power means, and which is provided with a fuel by-pass so as not to disrupt fuel flow during inoperation of the pump.

Other and further features and objects of the invention will be apparent to those skilled in the art from the following detailed description of the annexed sheets of drawings which, by way of preferred example only, embodiments of the invention.

0n the drawings:

Figure 1 is a diagrammatic view of the elements comprising an aircraft fuel system which incorporates an engine-driven mixed flow multiple pump having an impeller stage and a positive displacement vane-type pumping stage;

Figure 2 is an irregularly taken vertical crosssectional view of the mixed flow multiple pump of Figure 1, taken substantially as indicated by line II--II of Figure 1 so as to show internal structure of the pump at the vane stage and to expose the relief valve structure for the vane stage;

Figure 3 is a vertical cross-sectional view of the pump of Figure 2 taken in the plane of the longitudinal axis of the impeller and the rotary vane;

Figure 4 is a vertical cross-sectional view taken in theplane of the longitudinal axis of a modified mixed flow multiple pump having an impeller inlet stage and a positive displacement gear pumping outlet stage; 7

illustrate two specific periphery of the Figure 5 is a vertical cross-sectional view of the multiple pump of Figure 4 taken substantially as indicated by the line V-V of Figure 4 and showing the driving gears for the multi-stage Figure 6 is a vertical cross-sectional view taken substantially as indicated on the line VI-VI of. Figure 4 showing the fuel pumping gear chamber and the inlets and outlets thereto; and

Figure 7 is a cross-sectional view of the valve for maintaining a positive pressure in the seal chamber for the pump of Figure 4.

As shown on the drawings:

In Figure 1 the reference numeral It indicates generally an aircraft engine having a carburetor I l which properly mixes liquid fuel received from its fuel inlet duct l2 with air received from an air inlet stack [3. j The engine HI drives a fuel pump l4 which has an inlet fuel duct l5 connected to the outlet of an engine-driven mixed flow multiple pump it having an impeller inlet stage and a rotary, sliding vane outlet pumping stage. The inlet to the multiple pump 16 is connected to a fuel duct If in communication witha fuel cell booster pump l8. The booster pump I8 is disposed within a fuel cell I9 and is driven by an electric motor housed within the upper section of its casing 18a. The pump 18 is a highly efficient liquid-vapor separating centrifugal pump which receives fuel from the cell l9 through its lower screened section I32; and thereafter centrifugally separates the heavier liquid portion of the fuel and pressures the liquid portion to its outlet l8c which communicates with the fuel line H. The booster pump l3 has its inlet and outlet in constant communication to permit fuel to flow directly from its inlet to its outlet under pull of the pump l6 and for the pump It during inoperation of the booster pump 18.

The pump 16 has an irregularly shaped body casing 20 having an open ended channel 2| (Figure 3) for accommodating the moving parts of the pump [6 and their associated elements. An

internal annular shoulder 2% on the casing 20 receives the radial flange of a thrust bearing 22 near one open end 2la of the channel 2|. The

bearing 22 journals one reduced end portion 23a of a hollow shaft 23. The other end portion 230 of the hollow shaft 23 is also diametrically reduced and ,iournaled by a bearing 25 of similar configuration to the bearing 22. The end portion 230 is internally splined at 230' to receive a stub-driving shaft 23 to be described in more detail hereinafter.

An eccentric sleeve or pumping liner 21 is disposed between the thrust bearings 22 and 25 to embrace an enlarged diameter or vane pumping rotor section 23b of the shaft 23. The sleeve 21 embraces the pumping section 231) in close running relation at the top surface of the shaft The pump- 23.b of the shaft 23 has a plurality of radial slots for accommodating sliding vanes 24. During rotation of the shaft 23, the vanes 24 slide radially inwardly and. outwardly in the section 231) as their outer edges contact the inner eccentric sleeve 21. A dowel pin 28 projecting from the casing 23 into a keyway slot 21a in the eccentric sleeve 21 prevents radial displacement of the sleeve.

A sleeve or bearing spacer 29 thrusts against the bearing 25 on the side opposite to. the pump ing section 23?) of the shaft 23 and has a shoulder 29a for accommodating a bearing gasket 33. A counterbore 2% on the end of the sleeve 29 opposite the bushing receives a fuel seal collar 3| and a seal ring 32. The collar 3| embraces the shaft 23 about its splined end section 230 but will not rotate with the shaft 23. The collar seals the inside of the sleeve or bearing spacer 29 from the leakage of fuel during the pumping operation to be later described.

The casing 20 has a counterbore 2lb communicating with the channel 2! at the end opposite to the opening 21a. a closure plate 33 secured to the casing 23 as by The counterbore 2H) nests the cap screws 34 with its inner surface spaced from the internally splined end 230' of the shaft 23.

The closure plate 33 has a central aperture 33a. so as to embrace the stub shaft 23 in spaced relation. The plate 33 is counterbored on its inner surface about its aperture 33a to accommodate an annular graphite seal 35 which rides on an annular flange 26a of the shaft 26.

The shaft 26 has a projecting externally splined end portion 23b for driving connection with the aircraft engine or other driving mechanism. The internal end of the shaft 260 is also externally splined for driving connection to the internally splined portion 230' of the shaft 23.

The casing 23 has a plurality of radial channels 36 axially spaced a relatively short distance from the end closure plate 33 which are capped by the plugs 37. One of these plugs such as the lowermost one can be replaced with a drain tube to the aircraft slipstream for removal of any fuelleaking from the pump. The space drained by such a tube (not shown) is, of course, sealed from the pump by a seal unit 38 for the shaft 230 and collar 3| and by the seal 35 so that fuel from the shaft 26 cannot escape during the pumping operation.

A plug 39 is disposed in the hollow shaft 23 between the splined end 260 of the shaft 23 and the pumping rotor section 23b to seal communication therebetween. Another seal member 40. is also disposed about the end 230 of the shaft 23 so as to contact the inner surface of the flanged portion 230, of the shaft 26 for retaining lubricant in the spline chamber.

As the shaft 26 is rotated from its source of power, the rotary movement is imparted to the shaft 23 along its entire length to the end portion 23a which is journaled by the bearing 22 and which projects into the end opening 21a in the casing 2.0.

A stub shaft 4.! is ress fitted within the end section 23a of the shaft 23, for rotation therewith. A reduced diameter portion Ma. projects through the opening 2 la and is secured by a key 43 to the hub 42a of a mixed flow (radial and axial flow) impeller 42. A further projectingportion 4") of the stub shaft 41- of lesser diameter has a threaded end portion for receiving a locking nut 44 whichsecures theimpeller 42- from axial, movement on the shaft 4|. The impeller has mixedflow type vanes 22b which at their outer edges operate in close; running relation to a substantially annularly shaped inlet closure member 45 defining a fuel inlet 4.5a communicating. with the fuel line I]. The closure plate 45' is secured to the casing 20 as by cap screws lfi and. cooperates with the casing 29 to define. a volute chamber 41 surrounding the radially extending portions of the vanes l'zb I During operation of the'pump t6, fuelenters from the fuel line I1 through the inlet 45 and is centrifugally discharged by rotation of the impeller 42 into the volute chamber 41. The fuel is then pressured into a communicating channel 48 which communicates with the vane pumping inlet chamber 49. The chamber 49 is in communication with an inlet 58 (Figure 2) of the eccentric housing or vane pumping liner 21 which houses the pumping rotor section 231) of the shaft 23. The vanes 24 then pressure the fuel in a positive displacement process through an outlet 5| in the housing 21 into a vane pumping outlet chamber 52 in the casing 28. The casing 20 defines an outlet port 53 which is connected to the fuel communicating line I5 to the fuel pump I4.

A spring-loaded by-pass valve 54 closes the vane pumping inlet chamber 49 from the vane pumping outlet chamber 52 during normal operation. If the inlet pressure to the vane pump (which is the outlet pressure from the impeller pump) reaches a predetermined maximum, the by-pass valve 54 will be opened and fuel will pass from the chamber 49 to the chamber 52, by-passing the vane pump.

A relief valve, indicated generally by the reference numeral 55 (Figure 2), is provided in the event the outlet pressure of the pump I6 exceeds a predetermined maximum. The relief valve 55 is disposed above the casing 20 in communication with the vane pumping inlet 49 and the outlet chamber 52. A base 56 for the valve is secured to the top of the casing 28 as by bolts 51. The base 56 has a central bore 56a and a central section 561) disposed within the bore to provide a valve seat 560 which seats an axially movable valve plug 51 having a web 510; slidable in the base 56 above the valve seat 560. The plug 51 remains seated due to the pressure of a coil spring 58-acting between a well in the plug 51 and a well in the cap member 59- for the relief valve 55. The force of the spring 58 may be adjusted by a centrally disposed bolt-like member 68 which threads into a sleeve 6| having an annular flange 6Ia for receiving the top of the spring 58. A jam nut or plug 62 is threaded onto the screw 68 for locking against further adjustment of the spring 58.

The spring 58 is bottomed in the well of the plug 51 on an annular clip 63 which retains the central portion of an annular diaphragm 64. The peripheral margin of the diaphragm 64 is retained between the base 56 and the cap 59.

If fuel in the outlet chamber 52 of the pump I6 exceeds a predetermined maximum, pressure exerted on the plug 51 willcause the plug to shift axially upward against the pressure of the spring 58 from the seat section 562). The fuel will then be permitted to flow into the vane pumping inlet chamber 49 to relieve pressure at the outlet 53.

A plurality of circumferentially spaced bleeding apertures 51bare provided in the web51a of the plug 51 to hydraulically balance the space between the diaphragm 64 and web with the space beneath the web.

From the foregoing description it will be seen that fuel enters the pump I6 through the inlet 45 and is centrifugally discharged by the impeller 42 into the volute 41 which empties into the communicating channel 48 to the'vane pumping inlet chamber 49. From the vane pumping inlet chamber 49 the fuel is pumped under increased pressure by the vane pumping rotor 23b of the shaft 23 into its outlet chamber 52 which communicates by means of the line I5 to the engine-driven fuel pump I4.

It should also be understood that if the fuel during inoperation of the pump I6.

pressure in the vane inlet chamber 49 exceeds a predetermined maximum, the bypass ,valve 54 will open and the fuel will by-pass the vane pump 23b. A

However, there is also provided aby-pass' arrangement so that both the impeller and the vane pumping stage of the pump I6 may be by-passed This arrangement comprises a spring-loaded by-pass valve 65 (Figure 3) disposedin a by-pass channel 66 which communicates with the inlet 45 of the pump I-6. The by-pass valve 65 closes communication between the inlet by-pass channel 66 and the communicating channel 48. During inoperation of the pump I6 and/or thebooster pump I8, the main fuel pump I4 will create .vacuum pressure in the fuel lines, sufficient to draw fuel from the fuel cell I9 through the booster pump I8. The fuel pressure thus created by the engine-driven main fuel pump will be sufficient to open the bypass valve 65 and allow the fuel to pass from the inlet by-pass channel 66 into the communicating channel 48 and on to the vane pumping-inlet chamber 49. Since the vane pump is likewise not in operation the pressure on the fuel in the chamber 49 will not be opposed by outlet pressure 52 from the vane pump 23b (Figure 2) and will, therefore, open the by-pass valve 54 previously described. The fuel will then pass from the vane pumping outlet chamber 52 through the outlet 53 to the main fuel pump I 4 and engine III.

A modified structure indicated generallyv by the reference numeral 10 (Figure 4) may be utilized in place of the pump I6. The pump 18 comprises anv impeller inlet stage and a positive displacement gear pumping outlet stage. I The pump 18 has an impeller casing H which defines a volute 12, surrounding a mixed flow impeller 13 which is secured to a projecting end portion 14a of a hollow driven gear 14. The gear 14 is driven from a gear 15, connected by a stub shaft 16 to a hollow shaft 11, internally splined to receive a driving shaft 18 constructed similarly to the stub driving shaft 26 of the vane pump I6. The stub driving shaft 18 is, of course, connected to the engine or other power source. A closure plate 19 closes the impeller casing H and defines an inlet to the impeller 13.

The other end of the impeller casing H is secured in sealed relation to a casing section M which houses the stub shaft 16 of the gear 15 and a projecting hollow end portion 14b of the gear 14. The casing section 8| is secured at its other end to a pumping gear casing 82 which houses an upper pumping gear 83 integrally formed to the hollow driving shaft 11 and a lower pumping gear 84 which is hollowed and has integrally formed axially projecting end sections 84a and 84b. The axially projecting end section 84a receives a stub shaft 85 in press fitted relation. The stub shaft 85 is also brazed to the end section 840 and provides a journal for rotation of the bushing 14b press fitted into the gear 14. As the driving shaft 18 is rotated the hollow shaft 11, the integrally formed pumping gear 83, the stub shaft 16 and the driving gear 15 also rotate. The driving gear 15 drives the relatively smaller gear 14 on its associated stub shaft 85 and the hollow pumping gear 84. The impeller 13 rotates with the gear 14.

A pair of coil springs 86 are secured within the casing 8i to bottom against rings 81 and 88, respectively, and thrust against bearings 90 and 9| which surround the shafts 11 and 84a, respectively. Periphera1 flange portions 90a and 9Ia on the thrust bearings 98 and 9|, respectively,

7 thriistag'aifiSt the pumping gears 83' and 84', The other side ef'tl'ie gears 83 and 84, respectively, filii listagainst the bearings 92 and 93, Whih are secured within the casing structure 82.

'Th end of the casing 32 nearest the source of poweris closed by aclosure plate 94 similar to the closure plate 33 of the pump [6 and the drivifig- Shaft 18 and the hollow Shaft 11 are embraced by a collar 95 anda eal unit 96' simi-' lar to the collar 3| and seal unit 38 of the pump It.

During operation of the ump 10 the impeller 13-centrifugally discharges fuel taken from the inlet 80' under pressure into the volute 12. The fuel is pressured from the volute 12 into an axial communicating passageway Q1 (Figures 5 andG) to the gearpumping stage of the pum 10'. The fuel then em ties into the gear um ing chamber 99 defined between the pumping gears 83 and 84. Inserts Hi and NH within the casing member 82 surround the pumping gears 83 and 84, re spe'ctively, to keep the fuel from passing about the outer periphery of the gears. The fuel is pumped in the conventional manner by the pumping gears- 83 and Mints the outlet chamber i021 and into the line I tcthe engine-driven fuel pump M. H p As shown in Figurel, the seal chamber I03 is vented through passage not to a spring loaded valve ass'embly iilt having a valve 108 loaded by a spring I01 which, when closed, separates passage 04; from a passage I08 to the inlet chamber 98. If excessive leak down pressure exists in seal chamber ms, the" vtuve I06 will open against the springv load to discharge the leaked in fluid to the inlet 98'. However, the

spring loaded valve will always maintain a positive pressure above inlet pressure in the" seal chamber, and this pressure" can be controlled so as to not rise above a desired maximum by selectives'etting oftheconipreSs'ion of the spring lni; It will, of course, be understood'that the mixed new multiple pump of the type iiiustra teu by pump is and by the pum 10 could be utilized in installations other than in an aircraft fuel system. n

It will also be understood that modifications I and variations maybe effected without departing from the scope ofthe novel concepts of the presant invention.

We claiin as our invention: 1. A multiple pump unit comprising, a casin having an open-ended channel therethrough defining a fiuid'linletat' one end thereof, an annular pumping chamber surrounding said inlet,- a fluid passageway connecting said annular pumping chamber and a medial portion ofsaid openended channel; and an outlet communicating with said inedialporti'ori, means on said casing defining a gear pumping chamber adjacent said outlet, a drive shaft journal'edin said casing at the other end of said open-ended channel, a

impeller shaft journaled adjacent the inlet end of said casing, an impeller secured to said impeller shaft for (lo-rotation therewith, mixed-flow pumping. vanes on said impeller projecting into 3 drive shaft, aseccndpiimping gear journaled in said casing and having a hollow portion receiving one end of said impeller shaft, a first driving gear connected to said first pumping gear, and a second driving gear connected to said impeller shaft, said gears being in meshed relation, whereby fluid is pressured during rotation of said drive shaft by said impeller from said inlet through said annular pumping chamber to said gear pumpin chamber wherein it is subject to increased pressure and discharged to the casing outiet.

2'. A comprising a casing having a'series interconnected volute pumping chamber and in tersecting bores forming a gear pumping chain her with a pump inlet to said volute pumping chamber and a pump outlet from said'gear pump-5 said inlet and having their radial ends disposed adjacent said chamber, a first pumping gear iournal'ed in said. casing and engaged by said mg chamber, a driver gear rotatable in one of said intersecting bores having a driving conned tion projecting outside of said casing and a first coupling gear inside of said casing,a driven gear rotatable in the other" of said intersecting bores'and having a shaft extension fixed thereto for rotation therewith, and a centrifugal in!- peller in said volute umping chamber journaled.

on said shaft extensioii and having a second coupling gear meshing with said first coupling gear, said first and second coupling gears being sized with respect to one another to drive said centrifugal impeller at higher rotational s eeds than said driver and driven gears.

3. A pump comprising a casing having a Series interconnected volute pumping chamber and intersecting bores forming a gear pumping chain'- ber with a pump inlet to said volute pumping chamber and-a pump outlet from said gear pump ing chamber, a driver gear rotatable in one ,cf said intersecting bores having a driving cori nection projecting outside of said casing and a first coupling gear inside of said casing, a driven gear rotatable in the other of said intersecting bores and having a shaft extension fixed thereto for rotation therewith, and a centrifugal impeller in said volute pumping chamber journaled on said shaft extension and having a second con-- pl-inggear meshing with said first coupling gear, said: first and second coupling' gears 'beiri'g sized with respect to one another to drive said ceritrifugalimpeller at higher rotational speeds that said driver and driven gears, said coupling gears being constructed and arranged to rotate said driven gear and said centrifugal impeller in a common direction to riiirlifrliz'e' the relative rota: tional speed at the joiirnaled surfaces between said shaft extension and said centrifugal inipell'er.

References Cited-in the file ofthis patent U'Nr'rsn STATES PATENTS Number 

